Update: I’ve not tested myself, but the comment from Sombunall below points out that package names for the TFTP server and the DHCP server have changed since I wrote this post!
It’s often the case that there’s no easy way of installing a machine that doesn’t have any removable media. For instance, I have an old Compaq Deskpro EN that’s too old to support booting from USB, so using something like UNetbootin is out of the question. Luckily, there’s an an alternative, which is to PXE boot an installer over the network.